Last year I changed the ball joints of our truck and didn’t pay attention about the installation direction of the ball joints when pressing them into the axle. Therefore one of the grease fittings from the lower ball joints is to close to the axle to grease it with a standard grease gun coupler.
My first attempt was to file the coupler down on one side to fit it on the grease fitting but this did not work.
I bought this adapter for hardly to reach grease fittings.
This adapter has a sleeve (compare first and second image) which could be moved front and back to lock the adapter to the grease gun to avoid accidentally disconnection.
The following three images illustrate how the adapter is connected to the coupler of a grease gun.
The front of the adapter has a conus with a seal in it which is pressed straight on the grease fitting with moderate force and then the grease is pumped in with the grease gun. In my case it worked pretty good. This adapter could also be used to grease U-Joints.
Front and back view of the adapter: